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Old 11-20-2009, 10:06 PM
Def Def is offline
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Thumbs up HOW TO: Ultimate budget front LCAs

This is a rough how-to on how to make your front roll center and LCA length adjustable with quality components in the most budget minded and safe way possible.

Things needed: (MMC = McMaster-Carr = www.mcmaster.com)

1. Set of Godspeed FLCAs
2. 2 x 4 1/2" long Grade 8 3/4"-16 bolts MMC p/n: 91257A879
3. 2 3/4"-16 Grade C conical locking nuts MMC p/n: 92501A455
4. 1" OD x 0.75" steel bushings(or DOM tubing you cut and face) You can stack MMC p/n: 94773A780
5. 2 x AIB-12T bearings from QA1 ~$18-19/ea
6. 2 x M16x2mm chromoly rod ends from www.midwestcontrol.com Link: http://www.midwestcontrol.com/buy.php?item=2937

Tools needed:
1. Harbor Freight step drills help and are the cheapest way to get the sizes of drills you'll need to use, you can get the cheap set that's about $8 on sale that has a 3/4" max bit, then the other set that's more expensive and has 2 bits in it has one that's 1-3/8" max

3/4" step bit:



2. Snap ring pliers
3. Small ~1.5" diameter circular wire brush, or small sanding drum like used on a Dremel rotary tool
4. Some sort of rotary tool with a cutoff wheel
5. Cheap digital calipers(~$12 at Harbor Freight) are helpful, and if you don't have a set, they are actually useful on a ton of different stuff. Both of my sets are accurate to within 0.001"(their highest resolution) according to NIST gage blocks, so I think it's fine to use measurements as firm targets in this guide.
6. Spray paint to get rid of the nasty red paint on your new Chinese-made arms


Final picture just to give you an idea of what we're going after:



I don't have pictures of every step, as I assume if you're thinking of doing this you can do some basic work on stuff, but I'll offer a rough guide that will hopefully answer some questions.

Step 1: Remove the outside spherical bearing and inner rod end.

I used a few sockets and my bench vise. The outer bearing is actually teflon lined(surprisingly), but the outer bearing cups are way too tight, so it keeps them from rotating freely. Anyway, press it out, a bit of heat from a torch on the bearing cup helps if it's being stubborn(both of mine were).

Step 2: Take circular wire brush or sanding drum to the inner surface of the bearing cup. You want to open it up just slightly to about 1.498-1.499". Your AIB-12T bearings should be 1.500", so you just want it to be a light press fit in the bearing cup.

Step 3: The AIB-12T bearing has a very slightly wider race than the Godspeed bearing, this will usually prevent the snap ring from completely engaging the snap ring groove. Solution? Take a rotary tool with a cutoff wheel and make the snap ring groove wider. You want to make it wider towards the open end of the bearing cup to fit the wider race - this is obvious when you're looking at it, just thought it was worth mentioning. 2 of those sandstone cutoff wheels mounted together makes quick work of this step.

I don't know if it's completely necessary, but I also didn't like how big the overhang was on the top of the bearing cup(where it encloses the bearing). I took the 1-3/8" step drill and drilled it out a bit. I think I stopped 1 step from the 1-3/8" size. Use the next step to give it a bit of chamfer up top, which is something the Chinese did remember to properly copy from the Ikeya Formula arms. Opening this up gives you more articulation angle with the bearing, but after I installed everything I've got tons of room for stuff to articulate. Better safe than sorry.

Step 4: Press AIB-12T bearing into the bearing cup. Make sure it goes in with slight resistance, but will still move freely with a rachet handle or the like for torque after installation. Ensure snap ring still engages. I used a bit of Loctite 620 bearing mount to ensure the bearing was going no where, but this is optional if your snap ring is properly installed and things are a light press fit. If everything fits, go ahead and paint the arms and get rid of the nasty Chinese red leaded paint(just speculating on the lead paint, but I wouldn't be surprised).

Step 5: Grow some large attachments and get ready to drill your stock front spindle. Grab a drill and the 3/4" step bit. Make sure you get the orientation of the ball joint hole down. It angles towards the top of the spindle mount, so it's not just 90 degrees to the hub face.

Step 6: Drill out the Godspeed balljoint spacers to 3/4" ID. I also took off a bit of the narrow end since they have incorrectly put a chamfer on the inner ID which makes the material very thin there. More material on this face reduces the stress the small face is under by increasing the area, so I wouldn't be too shy with it since you can get the adjustment back with the shims. I faced mine down to a total height of 0.875", and 0.850" would probably get it closer to a 1" OD.

Step 7: I had to slightly face both the jam nuts on the inner rod end to get the arm as long as my stock S13 arms, which was my goal given the tight fender clearance I have with 17x9 +20 wheels and 255/40-17 NT-05s. You could accomplish this with a rotary tool and some patience as well, or just live with the ~1/4-3/8" longer control arm(probably good if it works with your setup). Here's a pic illustrating the reduction in width of the jam nuts(inner and outer hex pieces), the top piece is unmodified:



Overall shot next to some OE arms:



Otherwise, install the inner rod end and make sure the jam nuts are keeping things in place.

Step 8: Determine your spacing you want on the outer bearing. I started with around 1.625" total between the bottom of the spindle and the top of the bearing. Use some shims on the bottom of the spherical bearing to get the bolt head away from the bearing cup. My spacer is 0.300" and seems adequate. I wouldn't go any shorter than this, and might even lean more towards going longer if you had stacks of shims you were using.

Bolt it all up and torque everything to factory specs. The outer 3/4" bolt *SHOULD* be torqued to something near 280 ft-lbs with lubrication(yea, it's a BIG bolt). I thought this would probably get close to yielding the steel bushings, so I lubricated things with some spray silicone lube(WD-40 works too) and hit about 140-150 ft-lbs. As you can see, I ended up going with a "bolt-up" approach so I can change the spacer height without disassembling everything else, as the bolt would otherwise hit my struts before I got it out.

Overall shot again:



Underneath clearance:



You're done, enjoy your revised roll center. I plan on extending the spacing to about 1.875" from the spindle to the bearing edge and trying to get an angle measurement on the arms, but as it is, I think the roll center is somewhere around the crank to a few inches below the crank level when static. I took off my front sway bar at the same time and the car feels like it rolls less than with a stiffened front sway bar. Worth the effort IMO.


Optional things to do:

-I welded on small tabs to bolt up my SPL brake deflectors, which you probably see in a few pics, the arms didn't come this way, and the fluxcore popped a bit, so it's not the prettiest weld(so please no, you can't weld comments, I'm well aware of this!).
-My arms had a slight bit of surface rust on the inside, they were just never painted, so I'd hit them with some primer and paint inside
-I turned down the shims/bushings that sit right against the spherical bearing to give a bit more articulation. I aimed for 0.910-0.920"(later the shoulder size of the bearing). You'd probably still be ok without doing this step, but it's worth a mention in case you find things tight.
-I also went with some 1-7/16" normal snap rings I had lying around to give a bit more lower clearance, but again, probably not necessary.
-I added washers below the 3/4" nuts, but there is not enough area there to use a "normal" sized 3/4" washer. I drilled out a random washer I had lying around to 3/4" ID that was around 1.125-1.25" OD for each side. The nut should fit in the spindle fine though, and if it's a bit tight, just hit the edge of each hex with a file to clearance it some.
-If you want even more adjustment, then step up to a 4.75" bolt and use more spacing as desired(that's the beauty of using a bolt here).


Concerns I had and my reasoning:

As far as if a bolt is strong enough, every analysis I did, even REALLY worst case scenarios led me to believe a 3/4" Grade 8 bolt is grossly overkill for anything you'd see on the car. I imagine you'll rip the whole front quarter of the unibody apart before you start coming close to breaking that bolt. When you get it in your hand I think you'll understand just how big a 3/4" bolt is. For an idea of the strength of a 3/4" Grade 8 bolt, even with a single shear condition with 2" of spacing, simple analysis suggested that just ONE bolt could suspend MULTIPLE S13's.

The arms seem overall strong enough, and were reasonably well made. It sounds like there is a lot of modification going on here, and some might consider it easier to just go with a custom arm from the start. Yet when you actually get down to it there's only a couple of hours of real work in this guide, and all my designs for custom arms seemed like way more work and many more expensive tools. In the end, I decided to pay ~$160 to have most of the work done for me, then just modify it to my needs.

I've got the rears in the works as well.
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Old 11-20-2009, 11:10 PM
McCoy McCoy is offline
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Def, thanks for doing the time to do the detailed writeup .

Quote:
Originally Posted by Def View Post
I've got the rears in the works as well.
Good, I can't wait to put my RLCA's to use!
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Old 11-20-2009, 11:35 PM
Bumnah Bumnah is offline
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Very nice!
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Old 11-20-2009, 11:49 PM
Def Def is offline
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Quote:
Originally Posted by McCoy View Post
Def, thanks for doing the time to do the detailed writeup .


Good, I can't wait to put my RLCA's to use!
The way I'm leaning on the rear involves using the Godspeed bearings and shanks. I remember you saying your shanks were the wrong ones. In which case you can just fit in a COM-12T bearing back there and drill things out for a 3/4" bolt. The rear bearings are about 1.410" OD IIRC, and a COM-12T is 1.437". You'd just need to keep working at it to get the bearing holder about the right size, get it in there, and have at it. Can't remember the race width difference off hand, but at worst you'll just need a bit of Loctite 620 and it's in there for good.
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Old 11-21-2009, 08:28 AM
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Very cool...this is the final step I think. We've got a way to get some pretty good DA dampers on the cheap, and all the rubber in the suspension has been eliminated...geometry correction was all these cars were begging for. Gotta beat up on those E36s that come stock at a reasonable ride height!
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Old 11-21-2009, 09:46 AM
Scores240 Scores240 is offline
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So when you do this, spacing the ball joint from the spindle. To get the same ride height you have to lower the spring perch right?
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Old 11-21-2009, 10:27 AM
Def Def is offline
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Quote:
Originally Posted by GodspeedS13 View Post
So when you do this, spacing the ball joint from the spindle. To get the same ride height you have to lower the spring perch right?
How much you space that lower outer spherical bearing/ball joint has ZERO affect on ride height. You can do 1/2" of spacing or 5" of spacing and your car will sit at exactly the same height.
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Old 11-21-2009, 11:05 AM
Scores240 Scores240 is offline
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Quote:
Originally Posted by Def View Post
How much you space that lower outer spherical bearing/ball joint has ZERO affect on ride height. You can do 1/2" of spacing or 5" of spacing and your car will sit at exactly the same height.
ah that's right all the spacing is doing is moving the lca down which doesn't effect ride height.
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Old 11-21-2009, 12:38 PM
240sxTTC 240sxTTC is offline
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Great write-up. Thanks for taking the time to detail the mods.
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Old 11-22-2009, 11:24 AM
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Awesome Def, thanks for your time on this.

Anyone put a price on all this. just parts wise?

great tags too. lol
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